Nontarget analysis of natural flavor metabolites in tobacco extracts

Large-scale production of tobacco generates significant amounts of waste, making the reuse and recycling of tobacco waste crucial for sustainability. However, the high diversity of tobacco metabolites requires a comprehensive analysis of tobacco waste extracts, so as to optimize extraction selectivity and recovery. In this study, we thoroughly analyzed the metabolic composition of 168 tobacco extracts using nontarget analysis. The extracts were derived from 56 tobacco wastes covering all four major tobacco types: flue-cured, dark air-cured, Burley, and Oriental tobaccos. From each sample, we obtained three types of extracts, such as concretes, absolutes, and supercritical fluid extraction (SFE) oils, through various extraction protocols. By matching deconvolved experimental MS/MS spectra with databases, 587 metabolites were putatively annotated, which were categorized into 24 groups, including alkaloids, indoles, and flavor compounds. The metabolic compositions of extracts from dark air-cured and Burley tobaccos were found to be similar, whereas flue-cured and Oriental tobaccos contained more diverse flavor components. Notably, concretes of various tobaccos prepared with 70 %-ethanol contained similar amounts of addictive alkaloids. However, the absolutes obtained by sequential extraction of these concretes with 95 %-ethanol effectively removed alkaloids while modestly maintaining the flavor compounds. Conversely, extraction protocols incorporating supercritical fluid extraction followed by 95 %-ethanol extraction resulted in the loss of most flavor compounds, likely due to the incompatibility between the solvents used in the two extraction steps. In conclusion, our study demonstrates that absolutes derived through secondary extraction with varying ethanol-water ratios holds significant potential for utilization.